Immunolocalization of laminin in neoplasms of the central and peripheral nervous systems.

Laminin is a basement membrane glycoprotein that is expressed in vitro by immature and neoplastic astrocytes. The expression of laminin in vivo was examined immunohistochemically in normal adult brain and 90 neoplasms of the central and peripheral nervous systems. In normal adult brain, laminin was detected in the vasculature, arachnoid, pial-glial membrane, and choroid plexus. The vasculature in all 90 tumors demonstrated intense laminin immunoreactivity. Deposits of laminin were observed at the glioma-mesenchymal junction in several neoplasms, but never between or within neuroepithelial cells. The glial basement membrane often remained intact although surrounded on both sides by invasive glioma or medulloblastoma. However, there was always fragmentation and disruption of the glial membrane in adjacent fields. Laminin expression by tumor cells was observed in 10/10 schwannomas, 9/10 fibroblastic meningiomas, 3/19 nonfibroblastic meningiomas, and 3/6 mixed glioma-sarcomas. Laminin expression in the normal nervous system and in neuroepithelial neoplasms corresponds to regions of recognized basal lamina formation, including the junction between glial and mesenchymal elements. Although invasive gliomas are able to break down the pial-glial basement membrane and gain access to the perivascular or subarachnoid space, this membrane often remains intact late in the invasive process and may represent a partial barrier to tumor invasion. Laminin may be a useful marker for schwannomas, fibroblastic meningiomas, and vascular neoplasms of the nervous system.